Optical bistability and photon statistics in cavity quantum electrodynamics

The quantum statistical behavior of a small collection of N two-state atoms strongly coupled to the field of a high-finessse optical cavity is investigated. Input-output characteristics are recorded over the range 3≲N≲65, with bistability observed for N≳15 intracavity atoms and for a saturation photon number ${\mathit{n}}_0$≃0.8. For weak excitation the transmitted field exhibits photon antibunching as a nonclassical manifestation of state reduction and quantum interference with the magnitude of the nonclassical effects largely independent of N.